Can a rye cover crop facilitate early soybean planting?

PI: Laura Lindsey

Graduate Student: Seth Kannberg

This trial was established in fall 2020 with rye cover crop planting. Soybeans were planted the following year in spring 2021. Table 1 shows the cover crop and soybean planting dates at the two trial locations.

Results from Wooster in 2021. In Wooster, soybean plant stand and yield were influenced by the interaction of planting date x cover crop (Figure 1). Yield was greatest for soybean planted ultra early (April 6) without cover crop, early (April 28), and normal (May 26) without cover crop. Yield was lowest for soybean planted ultra early with a cover crop and normal with a late-terminated (planted green) cover crop. These yield reductions were likely due to low plant population, which was low when there was a cover crop.

Figure 1. Soybean yield by planting date and cover crop treatment at Wooster in 2021. Soybean plant stand is shown within each bar.

Results from South Charleston in 2021. In South Charleston, the main effect of planting date and main effect of cover crop significantly influenced soybean plant stand. For the ultra early and early planting dates, soybean stand ranged from 65,000 to 75,000 plants/acre. For the normal planting date, soybean stand was 100,000 plants/acre. In plots with the early-terminated cover crop, soybean stand was approximately 70,000 plants/acre and significantly reduced compared to the no cover control, which had an average plant stand of 85,000 plants per acre. At South Charleston, soybean yield was influenced by soybean planting date, but not cover crop (Figure 2). For the ultra early and early planting dates, soybean yield was over 70 bu/acre and reduced to just over 60 bu/acre for the normal planting date.

Figure 2. Soybean yield by planting date treatment at South Charleston in 2021. Average soybean plant stand is shown above each bar.

Key Take-Aways from the First Year.

1. This is one year of data and 2021 was an abnormally good year. This study needs to be repeated in 2022.
2. Planting date is important. In South Charleston the April planting dates yielded the same, but there was a reduction in yield when soybeans were planted in May. Our previously conducted planting date trials have shown similar results.
3. Effect of cover crop is variable. For yield, there was no effect of cover crop in South Charleston. However, the presence of a cover crop strongly influenced plant stand and yield for the ultra early and normal planting dates.
4. Soybean plants are very good at compensating for low populations. Even with a stand of ~20,000 plants/acre, yield was 55 bu/acre in Wooster.

This project was designed to test the hypothesis that ultra early soybeans may be protected from freeze events by cover crop residue. There were freeze events at both locations in mid-May. However, in Wooster, the cover crop had a detrimental effect on soybean. Plants were damaged by the freeze event and also (possibly) by slug damage. In South Charleston, the cover crop did not influence yield and the freeze event here resulted in less damage to soybean (just bronzing of the cotyledons).